Everyone says that buying a ganny fresh old car is the best. They are one owner, low mileage gems that granny ony drove to bingo and her Wednesday hair appointment. There can be a problem with driving nothing but short trips. Carbon builds up on the pistons, rings, and valves without longer trips where the engine gets higher rpms at longer periods of time to burn it off. Years later, a new owner gets this great car with a smooth running engine that is also using oil. That is a problem we are having with a low mileage ’73 Monte Carlo we are working on. It’s a great car. It runs and drives fantastic, but it’s 350 is going through the oil nearly as fast as gasoline.
We just replaced the original heads with freshly rebuilt set. We even spent the dough to have the valve guides machines for top of the line Viton seals. We solved the problem with the car smoking like a steam engine every second it’s running, but the oil useage remained. We thought that we’d need to pull the whole engine and rebuild the short block to solve this issue.
But first, we wanted to know what the hell is up. What was causing this. After talking with smarter people than us including our machinest, Garrick Preece at Kelly’s Block Welding, he said that the lack of long trips where the engine gets up to rpm and heat the carbon buildup on the piston rings can cause them to stick and not seal the engine. Add to that, the Monte Carlo sat for long periods of time with very little use; added up to lack of sealing in at least one of the cylinders. The picture below shows the pistons in our 350 as they looked when we changed the heads. Lots of carbon gunk on them.
We were looking for a fix that didn’t include an engine hoist and a machine shop bill. We’ve heard of all kinds of remedies over the years to help piston rings seals. From the old tale straight from GM telling service departments to pour Bonami down the gullets of the then new small block V8 to get the rings to seal (Yes, the legendary small block was an oil burner like the Ford flathead.); to the a couple quarts of diesel fuel in the crankcase. We haven’t seen Bonami on the shelves in twenty five years and putting fuel where the oil is supposed to go, frankly, scares us. There were other tried methods we’ve heard over the years. Marvel Mystery Oil in the cylinders, let it sit for a week. Revving the engine to 2000 rpm plus and spraying water down the carb. Transmission fluid in the crankcase. And, transmission fluid into the spark plug holes, let it sit for a few days, and fire it up. We chose the last idea.
But, before we started dumping tranny fluid down the cylinders, we decided to do a compression test to make sure we don’t have a completely dead cylinder. We also thought we might be able to locate the cylinder with the sticky rings. If you have never done a compression check before, it’s quite easy with the right tools. We got our compression tester from Sears toy department, Craftsman. It’s just a gauge and some adapters to fit different spark plug sizes.
First thing to do is to warm up the engine, then pull the plug wires, and spark plugs. We just draped the plug wires on top of the intake, out of the way.
Next thing to do is open the throttle of the carburator wide open. We just use the throttle return spring to hold it open like in the picture.
Then, screw the proper adapter into a spark plug hole and attach the gauge. Then it’s just a matter of cranking the engine. The gauge will go up with each compression stroke as the engine spins. Keep cranking the engine until the needle on the gauge stops climbing. It usually only take four cycles of the engine to get a final reading. Write down the number on guage and continue the process for all eight cylinders.
We ended up with pretty good readings on all cylinders. Most repair manuals say the cylinders should be within 15% high to low numbers. Our Monte’s 350 scored the following:
1. 150 2. 155
3. 150 4. 155
5. 155 6. 160
7. 155 8. 165
We didn’t get a low number, or a dead cylinder indication. We should’ve dug out our leak down tester at this point which is a better tool for finding leaky piston rings, but we were running low on time. We were going to continue with our remedy anyways, so we just got on with it. We got a quart of ATF and a flexible funnel and got to making a mess.
The funnel’s end is small enough to go through the spark plug hole. We poured about 3-4 ounces of ATF into each cylinder. One cylinder was at top dead center and the fluid just poured back out of the hole. So we clicked the starter a couple times to get the piston down in the hole far enough to take in the fluid. After getting ATF into every cylinder, we put the spark plugs back in. But, before reconnecting the spark plug wires, we cranked over the engine a few times in order to use the compression strokes to force the ATF into ring lands. This is very important. Only use a few ounces and don’t completely fill the cylinders. It can cause the engine to hydrolock if you tried firing it full of ATF.
Then it was just a matter of waiting a few days. The detergents in the transmission fluid should break up the carbon build up. Hopefully, the rings will get unstuck and seal the cylinders better. After a few days, we started up the car. As you can imagine having that much oil in the cylinders caused a bit of smoke. The car will smoke for a while. In order to get the car to clear up the billowing smoke faster, we took a 15 mile jaunt down the freeway. The first mile no one behind us could see through the smoke screen.
Here’s the Youtube video of the car as a gross polluter. Thankfully, most of our neighbors were at work so they couldn’t call CARB on our asses.
What was the result of this freebie fix? The jury is still out, but it looks like it’s a fail. We still see smoke when we are hard on the gas pedal. And, the oil level was down after a 80 mile trip on Sunday. But, we didn’t check the oil before the trip, so we’ll have to see. If it looks like a bust for sure, we’re planning to spray water down the carb with the engine running as a next step. This comes from noticing that cylinders with a blown head gasket always have sparkling clean pistons. We’ll keep you updated.
